The use of multi-user, radio communication systems have achieved wide popularity in recent years as advancements in communication technologies have permitted the affordable utilization of such radio communication systems by large numbers of users.
The communication channel connecting a sending station with a receiving station in a radio communication system is formed of a radio communication channel. A radio communication channel is defined upon a portion of the electromagnetic spectrum. Because a radio communication channel is used to communicate communication signals between the sending and receiving stations, a conventional wireline connection, required by conventional wireline communication systems, is not required to interconnect the sending and receiving stations to permit the effectuation of communications therebetween. The use of a radio communication system to communicate therethrough is of particular advantage when formation of a wireline connection between sending and receiving stations would be inconvenient or impractical.
A sending station of a radio communication system is operable to convert information which is to be communicated to the receiving station into a communication signal of characteristics which permits its communication upon the radio communication channel. To convert the information into such a communication signal, the sending station modulates the information signal upon a carrier wave of a carrier frequency within the range of frequencies which defines, at least in part, the communication channel. A radio device which provides both a sending station and a receiving station at a common unit is sometimes referred to as a radio transceiver. Two-way communication is permitted through the use of a radio transceiver.
A cellular communication system is exemplary of a multi-user radio communication system, usage of which has achieved wide popularity in recent years. When a user communicates by way of a radio transceiver, typically referred to as a mobile station, the mobile station is constructed to mimic the operation of a conventional, wireline telephonic device. Because telephonic communication is effectuated without the need of a wireline connection with the mobile station, the mobile station can be utilized to effectuate telephonic communications from locations at which formation of a wireline connection would be inconvenient or impractical.
With advancements in digital communication techniques, cellular, as other radio, communication systems increasingly are implemented which make use of such techniques. And, while conventional, analog cellular communication systems have been installed over wide geographic areas, additional cellular communication systems, making use of digital communication techniques, have now also been installed over wide geographical areas. The geographical areas encompassed by conventional, analog cellular communication systems and the geographical areas encompassed by digital communication systems regularly overlap. A user is oftentimes provided thereby with a choice of communication systems within a geographical area by which to obtain a service subscription to communicate by way of a selected cellular communication system.
Cellular communication systems are allocated with portions of the electromagnetic spectrum upon which to define communication channels to permit effectuation of communications. Generally, even in communication systems which provide for both conventional, analog communications and also digital communications, certain portions of the allocated frequency spectrum, allocated to the communication system, are used to effectuate analog communications and other portions of the allocated spectrum are utilized for digital communications. And, separate communication systems are allocated separate portions of the electromagnetic frequency spectrum. That is to say, a first frequency band is allocated for use by a first cellular communication system, and a second frequency band is allocated for communications pursuant to a second cellular communication system. Such frequency bands are sometimes adjacent to one another.
For instance, some existing digital cellular communication systems utilize Code-Division, Multiple-Access (CDMA) technologies. Such systems are implemented over wide geographical areas. Other cellular communication systems, such as AMPS (Advanced Mobile Phone Service) and TDMA (Time-Division, Multiple-Access) cellular communication systems are also installed over wide geographical areas. The geographical areas over which CDMA and AMPs or TDMA systems are installed generally overlap, at least to some extent.
The frequency band allocated to a CDMA system is generally dissimilar with the frequency band allocated to an AMPS or TDMA system. But, signals generated during operation of the AMPS or TDMA communication system might form interference to interfere with communication of signals in the CDMA communication system. Even though signal energy generated during operation of the AMPS or TDMA system might well not include components which fall within the signal bandwidth of a CDMA signal generated during operation of the CDMA system, the signal energy forming the interference might be of characteristics close enough to the center frequency of the CDMA signal to distort the CDMA signal.
If the interference caused as a result of such adjacent-band signal generation is not properly accounted for, misoperation of the receiver portions of the mobile station which receives the CDMA signal might result. Namely, analog-to-digital converters forming a portion of the receive portion of a mobile station might saturate due to the relatively low resolution levels of the analog-to-digital converters typically utilized in such mobile stations.
A manner by which better to compensate for adjacent-band interference forming a portion of a receive signal received at a mobile station would better ensure acceptable operation of the mobile station.
It is in light of this background information related to operation of radio communication systems that the significant improvements of the present invention have evolved.